This paper describes a conditional simulation technique that constrains areal permeability fields to typical statistical information and indirectly to waterflood well performance. Near-well effective permeability and reservoir connectivity characteristics are used as indirect well-performance constraints. Results are validated by examining simulated waterflood performance of a five-spot pattern. This technique can be used to reduce the uncertainty of future well performance significantly. Additionally, the effect of alternative operating scenarios, such as infill drilling, can be evaluated more realistically.